Prioritisation of Emerging Contaminants for Monitoring in Indian Aquatic Environments Based on Occurrence, Treatment Persistence and Ecological Risk

Emerging contaminants (ECs) comprise a heterogeneous group of substances that are not routinely addressed within conventional environmental monitoring programmes but may enter aquatic systems and exert ecological or other environmental effects. Pharmaceuticals, personal-care products, endocrine-disrupting chemicals, antibiotics and related compounds are of particular interest because their continuous use and discharge can create repeated inputs to wastewater and receiving waters. Their environmental significance cannot be inferred from concentration alone because persistence, biological activity and toxicity vary substantially among compounds (Fent et al., 2006; Tang et al., 2020; Ortúzar et al., 2022).

Wastewater is an important pathway for the transfer of ECs to aquatic environments. Conventional wastewater treatment plants were designed primarily for removal of conventional organic matter, nutrients and pathogens, rather than the broad range of trace organic micropollutants now routinely detectable by modern analytical methods. Consequently, treatment performance varies markedly among contaminants and treatment configurations. Indian investigations have documented both substantial removal for some compounds and limited, negligible or even negative apparent removal for others (Subedi et al., 2015, 2017; Singh & Suthar, 2021b; Dubey et al., 2023).

Occurrence is therefore only one dimension of monitoring relevance. A contaminant detected repeatedly may warrant attention because of widespread environmental presence, whereas another compound with fewer occurrence observations may warrant attention because its reported ecological-risk quotient is substantially higher. Multi-criteria approaches have been used internationally to address this problem by combining occurrence, persistence, hazard and other characteristics rather than relying on a single indicator (Gaston et al., 2019; Wielens Becker et al., 2021).

The Indian evidence base is sufficiently developed to demonstrate widespread occurrence, but it remains heterogeneous in geographical coverage, environmental matrix, analytical target list, wastewater-treatment technology and ecological-risk methodology. Studies have investigated the Yamuna, Ganges and Cauvery river systems, urban lakes, municipal wastewater, sewage treatment plants and decentralized greywater systems, but the resulting evidence is fragmented across individual contaminants and evidence dimensions (Ramaswamy et al., 2011; Mutiyar et al., 2018; Singh & Suthar, 2021a,b; Biswas & Vellanki, 2021; Renganathan et al., 2021; Biswas et al., 2024).

The present study addresses this gap by developing a transparent quantitative framework for monitoring prioritisation in Indian aquatic environments. The framework integrates occurrence, treatment persistence and ecological risk, assigns explicit weights to the three dimensions, and tests the sensitivity of the resulting priorities to alternative weighting assumptions. The objective is not to establish a definitive national ranking of environmental hazard, but to provide a reproducible screening tool that converts fragmented Indian evidence into a practical set of monitoring priorities.